Lately I've noticed that if I apply too much power from a standstill, the gearshift from 1st to 2nd is a bit harsh. It's a classic symptom of a clogged filter mesh (the restriction causes low fluid pressure, the resultant sloppy shifts are most noticeable in the lower gears). I suspect I'm only noticing it recently because I've tuned the engine to make a wee bit more power than it used to. Living at the bottom of a steep hill probably doesn't help.

Time to replace the mesh filter. While taking pictures. But first, a bit of research into our Automatic gearboxes.

Mitsubishi call our transmission an V4AW2, but it's made by Aisin AW and fitted to a great many vehicles, not just Mitsubishis. Toyota call it an A44DL or an A45DL, depending on the clutch packs fitted. Dodge (and most of the internet forums) call it an AW372L. Aisin's ID plate calls it an AW03-72L. Some manufacturers (Volvo in particular) fit it with a proper paper filter as well as the mesh filter, but Mitsubishi and Toyota just fit the mesh. Incidentally, the "L" in the Aisin model number means it has a lockup torque converter. Not all L300s had this. The best way to check is to look at your transmission's ID plate:

TransPlate.JPG (52.62 KiB) Viewed 1227 times

("91" is the year of manufacture, "D" means April (A=January and so on) and 65014 is the actual serial number.

Righto. On with the messy bit.

Drain the transmission fluid from the pan.

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Detach the dipstick tube- there's a single 12mm bolt near the top. The tube has an O-ring where it joins the pan, and it can be difficult to separate the two- it's much easier to do it from above, rather than from underneath while it's raining ATF on you.

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DipstickTubeOut.jpg (50.01 KiB) Viewed 1227 times

Remove the pan- take note of how loose the 10mm bolts are. They should be little more than hand tight (4.5Nm/3.3ft.lb). From the factory the transmission had a gasket, and if yours is still there it should come away cleanly and be re-usable. If it's been replaced with silicone gasket then you're going to have to gently cut the pan off.

DrippyBits.JPG (51.08 KiB) Viewed 1227 times

Unbolt the mesh filter from the underside of the transmission and replace with a new one. Again, note that the 8mm bolts holding it on are little more than hand tight (5.5Nm/4ft.lb). Take care when removing the screen- there's about a pint of ATF trapped above it, and it all falls down -sploosh!- when the screen comes off. I didn't take photos of this bit because it was raining transmission fluid under there, but here's the new screen and gasket before installation (and the old one with gunk visible on the mesh):

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Next clean the pan and the two magnets, while being thankful there aren't any large metal shavings or gunge in there:

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PanCleaned.jpg (57.25 KiB) Viewed 1227 times

Reinstallation is the reverse of removal, unless you've damaged the gasket, in which case you'll have to clean up the flange surfaces and use silicone gasket maker to seal the pan.

Reinstall the dipstick tube, and refill the transmission through it.

In my case, the old filter was more than half clogged- and with the new filter the gearshifts are back to normal. Phew!

A workshop manual is your friend here, but I used Dexron 2 compatible transmission fluid (Dexron 3 is usually compatible with Dexron 2, but check what it says on the label before buying). I believe a complete fluid change uses about 7 litres, but just pulling the oil pan used about 4 litres. I bought the parts from Amayama.com, but any Mitsubishi dealer should be able to order them in if you give them the Mitsubishi part numbers.

Growlerbearnz wrote:A workshop manual is your friend here, but I used Dexron 2 compatible transmission fluid. I believe a complete fluid change uses about 7 litres, but just pulling the oil pan used about 4 litres. I bought the parts from Amayama.com, but any Mitsubishi dealer should be able to order them in if you give them the Mitsubishi part numbers.

You're using Dex II?? Everyone here is using Dex III.

Falco.

Sent from my smart pad, using a pen.

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Well.... To avoid confusing the issue I've said Dexron II because that's what the workshop manual and markings on the drain plug specify, though I've been a bit weasly and put the word "compatible" in there to cover my ass.

In reality, straight Dexron II is hard to find. All Dexron III fluids are Dex II compatible, and should say so on the pack. A mechanic or salesperson should be able to explain this to anyone asking for Dex II fluid. Yes, I'm using Dexron 3. Reply updated

I recently had my transmission rebuilt. New clutch packs, bearings, the lot. The rebuilder refilled with Dexron VI which is a synthetic, and supposed to be backward-compatible with Dexron III. It's a lot thinner than Dexron III for efficiency purposes, and being a synthetic is more resistant to heat.

I found the Dexron VI to be awful. Harsh shifts, higher torque converter stall speed (engine revving higher than usual when starting off, wasting all that lovely diesel torque), and more slip when it was hot. I switched back to a synthetic Dexron III (Mobil 1) and all is well again.